Blender 2.80 fix normals after boolean
Your topology is bad, you have a lot of ngons, you need quads. What you could do is correct your object this way:


Apply the rotation of your object. Only keep a section, delete the rest:





Create an empty at the origin of your object:





Give your object an Array modifier with the empty as Offset Object. Enable Merge and First Last options:





Rotate your object so that it makes a complete circle:





Correct your topology with the knife or with some joins so that it is made of nice quads, create some bevels, etc (here just the beginning before my computer crashed):